Experimental Shigellosis in Mice

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Abstract
The authors were able to infect mice orally only with virulent shigella mutants selected on the basis of the refractivity of agar plate colonies. These mutants gave also rise to keratoconjunctivitis in guinea pigs. Infection of the mouse resulted in a prolonged symptomless excretion, beginning about 1 hr. after the administration of the causative agent. The small intestine was transiently free from shigellae. The coli flora exerted a considerable, but not absolute defence against infection. Mice depleted of their coli flora by streptomycin treatment could be infected with a few cells of virulent mutants. Superinfection of shigella-excreting mice with E. coli resulted in a reduction in the number of excreted shigellae. Shigellae invaded the lymphatic tissues of the intestinal wall. Sometimes they were isolated from mesenteric lymph nodes. Bacteriaemia and their presence in the liver or spleen were never observed. Infection with shigellae resulted in gradually increasing protective serum antibody tltres and rapidly rising high protective coproantibody titres. The experimental findings are discussed and the suitability of mouse model experiments in studying the problems of human dysentery have been pointed out.